A vehicle differential is a device employing differential gears within a housing called a differential carrier. The vehicle differential is connected to three shafts. An input shaft transmits torque and rotation from a vehicle engine into the differential gears. In turn, each of the other two shafts separately transmits a portion of the torque and rotation from the differential gears out to separate external wheels.
For lubrication of the meshing of the differential gears, the differential gears within the differential carrier are at least partially submerged in a lubricant, for example, a mineral—standard base lubricant or a synthetic—premium lubricant. In either case, the lubricant may be certified as an API GL5 classification oil or SAE J2360 standard oil, and sealed within the differential carrier housing.
As a result of initial machining of the differential and associated parts therein, along with rigorous meshing of the differential gears during the differential's operation over an extended period of time, metal particles enter the lubricant within the differential and cause friction within. In turn, the friction affects the thermal conditions by increasing the temperature within the differential, which in turn causes more wear on the associated parts.
In general, when the rear wheels of a vehicle are caused to turn or are experiencing wheel slippage, as quite often happens, an outside wheel(s) makes a larger radius than an inside wheel(s). As a result, the outside wheel goes a farther distance, moves faster, and turns more revolutions than the inside wheel. Consequently, when both wheels are on the same axle shaft, one or both wheels would have to skid or slip to make a turn. However, by applying a differential between the rear wheels, the wheels are allowed to turn at different speeds.
As a vehicle operates, the meshing and rotation of differential gears, along with the presence of metal particles in the oil of the differential, friction increases. This results in heat building up within the space, oil, and parts that comprise the differential. Consequently, the differential experiences temperature swings and potentially extreme operational temperatures that can lead to part failures. Hence, it would advantageous to know the thermal conditions within the differential carrier, in order to detect potential part failures and long term reliability problems.
Even with these extreme conditions it is necessary to control and sense various solenoids, actuators, and sensors that are disposed on or within the differential carrier, which are used as locking mechanisms, fluid flow control valves, and clutch mechanisms. Unfortunately, electronic circuits that are needed to control such solenoids, actuators, and sensors cannot withstand being conventionally mounted on differential carriers, where they would be needed. This results in reducing or even eliminating the effectiveness of such controls.
Consequently, it would be beneficial to provide a means to monitor the thermal conditions within a differential, while using a packaging with standard electronic controls therein that would be able to function properly at or even within the extreme conditions presented by a differential carrier. Such a monitoring means needs to be directed to electronic controls that would include sensing solenoids, actuators, sensors, and the like that are disposed on or within a differential carrier.